The German laid-open specification DE 19705228 A1 has disclosed an AC generator which has an arrangement comprising a rotor and a stator, it being possible for the rotor to be energized by its field coil by means of a slipring arrangement at the right-hand end of the shaft. Carbon brushes slide on this slipring arrangement. In order to protect against external environmental influences, this slipring assembly is protected from the ingress of water (for example cleaning of the motor of the motor vehicle by means of a high-pressure cleaner) by means of a fitting sleeve. Secondly, it is desirable for eroded material from the carbon brushes which necessarily occurs during operation to be removed from this fitting sleeve.
U.S. Pat. No. 5,625,244 has disclosed an arrangement which produces a draught of air through a corresponding fitting sleeve by means of one of the fans which cool the stator windings. The disadvantages of this are that the efficiency is only unsatisfactory and, in addition, longitudinal slots introduced into the bearing section influence the bearing arrangement of the entire electrical machine.